It is well known that 5HT (hydroxytryptamine, serotonin) is a neurotransmitter in the living body. Three types of receptors which are related to 5-HT are known, and they are called 5-HT.sub.1, 5-HT.sub.2 and 5-HT.sub.3 type receptors.
5-HT.sub.3 receptors are widely distributed in the brain, heart and digestive canal, and 5-HT has an activity with respect to these receptors as a mediator.
It is confirmed that when 5-HT acts on 5-HT.sub.3 receptor at the peripheral nerve, pain and bardycardia are induced; and on the other hand, when 5-HT acts on 5-HT.sub.3 receptor at the central nerve, mental action e.g. emotions, appetite and memory, are induced. Further, 5-HT acts on 5-HT.sub.3 receptor at CTZ (chemoreceptor trigger zone) in the brain, nausea and vomiting being induced.
So it is thought that 5-HT.sub.3 receptor antagonist is useful for the prevention and treatment of central nerve diseases such as schizophrenia, corpulence, mania, anxiety, gastroenteric functional defects such as peptic ulcer, peptic esophagitis and migraine, vertigo, nausea and vomiting (especially vomiting induced by administration of an anti-cancer agent such as cisplatin).
It was known that large scale administration of Metocraplamide, which acts with side effects only, suppresses vomiting induced by an anti-cancer agent, and that other anti-vomiting agents are not effective.